Metric Sobolev spaces I: equivalence of definitions

Fuente: arXiv
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Autores principales: Ambrosio, Luigi, Ikonen, Toni, Lučić, Danka, Pasqualetto, Enrico
Formato: Preprint
Publicado: 2024
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author Ambrosio, Luigi
Ikonen, Toni
Lučić, Danka
Pasqualetto, Enrico
author_facet Ambrosio, Luigi
Ikonen, Toni
Lučić, Danka
Pasqualetto, Enrico
contents This is the first of two works concerning the Sobolev calculus on metric measure spaces and its applications. In this work, we focus on several notions of metric Sobolev space and on their equivalence. More precisely, we give a systematic presentation of first-order $p$-Sobolev spaces, with $p\in[1,\infty)$, defined over a complete and separable metric space equipped with a boundedly-finite Borel measure. We focus on three different approaches: via approximation with Lipschitz functions; by studying the behaviour along curves, in terms either of the curve modulus or of test plans; via integration-by-parts, using Lipschitz derivations with divergence. Eventually, we show that all these approaches are fully equivalent. We emphasise that no doubling or Poincaré assumption is made, and that we allow also for the exponent $p=1$. A substantial part of this work consists of a self-contained and partially-revisited exposition of known results, which are scattered across the existing literature, but it contains also several new results, mostly concerning the equivalence of metric Sobolev spaces for $p=1$.
format Preprint
id arxiv_https___arxiv_org_abs_2404_11190
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Metric Sobolev spaces I: equivalence of definitions
Ambrosio, Luigi
Ikonen, Toni
Lučić, Danka
Pasqualetto, Enrico
Functional Analysis
Analysis of PDEs
Metric Geometry
49J52, 46E35, 53C23, 46N10, 46E15, 31C15, 28A12, 26A46
This is the first of two works concerning the Sobolev calculus on metric measure spaces and its applications. In this work, we focus on several notions of metric Sobolev space and on their equivalence. More precisely, we give a systematic presentation of first-order $p$-Sobolev spaces, with $p\in[1,\infty)$, defined over a complete and separable metric space equipped with a boundedly-finite Borel measure. We focus on three different approaches: via approximation with Lipschitz functions; by studying the behaviour along curves, in terms either of the curve modulus or of test plans; via integration-by-parts, using Lipschitz derivations with divergence. Eventually, we show that all these approaches are fully equivalent. We emphasise that no doubling or Poincaré assumption is made, and that we allow also for the exponent $p=1$. A substantial part of this work consists of a self-contained and partially-revisited exposition of known results, which are scattered across the existing literature, but it contains also several new results, mostly concerning the equivalence of metric Sobolev spaces for $p=1$.
title Metric Sobolev spaces I: equivalence of definitions
topic Functional Analysis
Analysis of PDEs
Metric Geometry
49J52, 46E35, 53C23, 46N10, 46E15, 31C15, 28A12, 26A46
url https://arxiv.org/abs/2404.11190